Introduction:

This is a serum enzyme produced by the bones (and reflective of bone-growth activity), the liver, and the placenta. In growing persons, elevation often reflects normal bone growth; and we used to "heat fractionate" the patient serum into the "heat stable" and "heat labile" (bone) components. If an elevated AP became normal after the serum was heated at 56 degrees C., the elevation was presumed to be due to a bone source.

Interpretation conventions or cautions:

Now, if AP is elevated and GGT/GGTP is not elevated, the AP elevation is presumed due to a bone source.

Test results:

• within normal range: (pending)
  1. normal people
  2. certain cases of metastatic neoplasia into liver and/or bone 
• elevated:
  1. liver disease (liver fraction of AP...heat stable):
  • obstructive jaundice (even pericholangitis as in abdominal inflammation...IBD-UC)
  • hepatocellular jaundice
  • hepatic venous outflow obstruction with biliary changes can give AP >1000⁴
  • space occupying liver lesions, diffuse or segmental
  2. bone disease (bone fraction...heat labile):
     • tumors
     • increased bone turnover (hyperparathyroidism; rickets; Paget's disease; healing fractures)
  3. placental disease (syncytial trophoblastic fraction...PLAP):
     • pregnancy (especially 3rd trimester).
     • ovarian, testicular, and germ tumors.
  4. other:
     • intestinal epithelial damage (strangulation/obstruction).
     • kidney/renal tubule damage/tumors...RCC.
     • hyperthyroidism²
     • congestive heart failure.
     • 1-3 weeks after pulmonary infarct.
     • pancreatitis.
     • CMV & EBV mononucleosis.
     • dozens of medications³
• decreased:

1. hypothyroidism
2. pernicious anemia/low serum B12 (osteoblasts need T4 & B12)
3. milk alkali syndrome
4. malnutrition
5. hypophosphatasia of any cause
6. celiac disease
7. Whipple disease
8. folic acid deficiency
9. hypoparathyroidism
10. lactosuria
11. chondrodystrophy
12. zinc deficiency of any etiology (dialysis or TPN, etc.)
13. trifluoperazine

Test synonyms: AP; alk phos.

References:

1. 1. Interpretative Pathology...the Lufkin Difference, R. L. Reece, M. D. 1977
2. Becker's Endocrinology (p1509) (Military Med. 148:548, 1978) & Am. J. Gastroent. 89:1071, 1994.(CP-96-13)
3. Clinical Chemistry vol. 18, Oct. 1972.
4. Batts KP, et. al. Histologic Changes Mimicking Biliary Disease in Liver Biopsies With Venous Outflow Impairment, Modern Pathology 17(7):874-878, July 2004.
5. hepatic lab tests, Practice Guidelines, National Academy of Clinical Biochemistry (NACB), USA.